Ok I've read this post many times and I think what you are trying to say is 1. Exploud has to rely predicting switches to beat it's counters and 2. Boomburst can be stalled out because it doesn't have infinite PP.I can't say I've had this problem specficslly but by those numbers couldn't slowking stall out boomburst with a few proper switches for regenerator? Switching into... Well.. any steel type with reasonable special bulk (doesn't get the garunteed 3hko on aggron locked into boomburst, stelix with no Special defense investment gets 3HKOed at best by it, brongzong laughs, and escavalier misses the 2hko even without assault vest.) Add in that all three of explouds other typical coverage moves do less than 20% to 252/96+ slowking (the one you stated in your example) and you would think that slowking dropping has made exploud much less viable as there is now a fairly solid answer to the choice speced version to both its main stab (almost anything that resists it can take it a few times) and to any of its coverage moves in slowking, who can heal off the damage easily with either regenerator or slack off. Of which using the latter exploud locked into the wrong move becomes set up fodder for calm mind varients. And if played properly and carefully can even take on it locked into boomburst as at +1 with the 252/96+ example you used the 2hko is not garunteed after leftevers recovery.
All in all I think that having such a solid answer to its coverage moves, one of the big things that makes it so threatening as it can OHKO most of the mons that can switch into its STAB, exploud has gotten weaker on the whole.
The second part is true, but that's true for literally every wall breaker. Besides for a move of its strength, Boomburst actually has a lot of PP. Also because Slowking is able to pivot in to scout of a coverage move simply means that it now gets a damage on Slowking and and the steel type you'd go into next. Relating to the second part, I don't think people realize just how spammable of a move Boomburst actually is. There are no immunities in Exploud's case, no 4x resist and every BB switchin lacks their own recovery. Exploud's main issues are its speed and typing. But because right now I've been seeing lot of balanced lacking Wish passers and teams with Steelix as their only actual BB resist, I agree that Exploud should rise to A-. I also think Silk Scarf Exploud is probably it's better set but I haven't had the time to test it throughly.